It started life as a Harvard course, then evolved into a television series, and finally completed its evolution by becoming a book. The book's core question - why did Europe and North America become so much richer and more powerful than the rest of the world? - is one I've been grappling with as a teacher for more than 20 years. It was time to pull all the threads together.

2. What was most difficult about it?

Deciding what to leave out.

3. What did you most enjoy?

Probably holding the original manuscript of Frederick the Great's Anti-Machiavel and reading Voltaire's marginal comments.

4. How long did it take?

Two years to write, 20 to research.

5. What has changed for you, since it was first published?

My fourth child, Thomas, came into the world.

6. Who's your favourite writer?

At the moment I am in the grip of Dickens mania, re-reading all the major novels.

7. What are your other inspirations?

My family. Wagner. Bordeaux. Arsenal. Swimming in the sea. And the thought of confounding my enemies.

8. Give us a writing tip.

Don't be prissy about it. You can write in the back of mini-van on a dirt track if you really have something to say - and a deadline.

9. What, if anything, would you do differently if you were starting he book again?